TCP and UDP are the core protocols of the transmission layer. The main difference is the data transmission method: TCP focuses on reliability and establishes connections through three handshakes to ensure orderly delivery, error checking, traffic control and congestion control, and is suitable for web page loading, email and other scenarios; UDP prioritizes speed, no connection is required, and does not guarantee delivery order or integrity, and is suitable for real-time applications such as video streaming and online games. The selection basis is: the accuracy and orderly delivery of TCP is required, and the UDP is pursued for low latency and real-time interaction. The two have their own advantages in different application scenarios.

TCP and UDP are two core protocols in the transport layer of the Internet protocol suite, and they play different roles in data transmission. The main difference between them lies in how they handle data delivery—TCP focuss on reliability, while UDP prioritizes speed.

TCP: Reliable Connection-Oriented Communication

TCP (Transmission Control Protocol) establishes a connection before sending data, ensuring that packets arrive in order and without errors. This is done through a process called the "three-way handshake." Once the connection is established, TCP monitors every packet sent, waits for confirmation from the receiver, and retransmits any lost packets.

• Ordered delivery: Packets arrive in the same order they were sent.
• Error checking: Each packet includes a checksum to detect corruption.
• Flow control: Adjusts the sending rate based on the receiver's capacity.
• Congestion control: Slows down transmission if network congestion is detected.

This makes TCP ideal for applications where accuracy matters more than speed—like loading web pages, sending emails, or transferring files.

UDP: Fast and Connectionless

UDP (User Datagram Protocol) doesn't establish a connection before sending data. It simply sends packets (called datagrams) without waiting for acknowledgment. That means some packets might be lost, duplicated, or arrive out of order.

• No handshake: Data can be sent immediately without setup.
• Minimal overhead: No tracking or retransmission of lost packets.
• Unordered delivery: Datagrams may arrive in any order or not at all.

Because of its simplicity and low latency, UDP is used in time-sensitive applications like video streaming, online gaming, or voice calls, where losing a few packets is less of an issue than delay.

When to Use TCP vs UDP

Choosing between TCP and UDP depends on what you're trying to achieve:

If your application needs:

• ? Accuracy and completeness — go with TCP.
• ? Ordered delivery — use TCP.
• ? Low latency over reliability — choose UDP.
• ? Real-time interaction — UDP is often better.

For example:

• Web browsers and email clients use TCP.
• Streaming platforms and VoIP services prefer UDP.

In practice, many applications use both—like video conferencing apps that use TCP for control signals and UDP for the actual audio/video stream.

A Quick Comparison Summary

So depending on whether you need guaranteed delivery or fast transmission, you can pick either TCP or UDP accordingly.

Basically that's it.

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